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Hybrid organic–inorganic perovskite (HOIP) materials have attracted significant attention in photovoltaics, light emission, photodetection, etc. Based on the prototype metal halide perovskite crystal, there is a huge space for tuning the composition and crystal structure of this material, which would provide great potential to render multiple physical properties beyond the ongoing emphasis on the optoelectronic property. Recently, the two-dimensional (2D) HOIPs have emerged as a potential candidate for a new class of ferroelectrics with high Curie temperature and spontaneous polarization. Room-temperature solution-processability further makes HOIP a promising alternative to traditional oxide ferroelectrics such as BaTiO3 and PbTiO3. In this perspective, we focus on the molecular aspects of 2D HOIPs, their correlation with macroscopic properties, as well as the material design rules assisted by advanced simulation tools (e.g., machine learning and atomistic modeling techniques). The perspective provides a comprehensive discussion on the structural origin of ferroelectricity, current progress in the design of new materials, and potential opportunities and challenges with emerging materials. We expect that this perspective will provide inspiration for innovation in 2D HOIP ferroelectrics. [ABSTRACT FROM AUTHOR]

Low-grade thermal energy, either from waste heat or from natural resources, constitutes an enormous energy reserve that remains to be fully harvested. Harvesting low-grade heat is challenging because of the low Carnot efficiency. Among various thermal energy harvesting mechanisms available for capturing low-grade heat (temperature less than 100 °C), the thermomagnetic effect has been found to be quite promising. In this study, we demonstrate a scalable thermomagnetic energy harvester architecture that exhibits 140% higher power density compared to the previously published spring–mass designs. The alternating force required to oscillate the thermomagnetic mass is generated through the interaction between two magnetic forces in opposite directions. We employed numerical modeling to illustrate the behavior of a thermomagnetic device under different operating conditions and to obtain the optimal hot-side and cold-side temperatures for continuous mode operations. A miniaturized thermomagnetic harvester was fabricated and experiments were conducted to systematically evaluate the performance. The prototype was found to exhibit an oscillation frequency of 0.33 Hz, a work output of 0.6 J/kg/cycle, and a power density of 0.2 W/kg of gadolinium under the temperature difference of 60 K. [ABSTRACT FROM AUTHOR]

VO2 thin films were grown on conducting oxide underlayer SrRuO3 buffered SrTiO3 (111) and Si/SiO2 substrates, respectively, using sputtering. X-ray diffraction phi-scans revealed the epitaxial nature of the VO2 films grown on SrRuO3 buffered SrTiO3 and polycrystalline structure for films grown on SrRuO3 buffered Si/SiO2. X-ray photoelectron spectroscopy confirms a dominant presence of V4+ in both films and establishes a high-quality growth of single-phase VO2 films. Temperature and electric-field driven metal-insulator-transition in both the in-plane and out-of-plane configurations were investigated. Depending on the configuration, the resistance change across the metal-insulator-transition varies from a factor of 1.57–3. The measured resistance in each state as well as the magnitude of resistance change were similar during temperature and electric-field driven metal-insulator-transition. To shed light on the suppressed metal-insulator-transition characteristics due to the current shunting effect from conducting SrRuO3 bottom electrode, a distributed resistance network model is proposed and benchmarked against reports from the literature. The results demonstrate the growth of high-quality VO2 on conducting SrRuO3 layers and their electrical behavior, which is of particular interest for all-oxide electronic devices utilizing phase transitions such as resistive memory and neuromorphic oscillators. [ABSTRACT FROM AUTHOR]

Future advancements in three-dimensional (3D) electronics require robust thermal management methodology. Thermoelectric coolers (TECs) are reliable and solid-state heat pumping devices with high cooling capacity that can meet the requirements of emerging 3D microelectronic devices. Here, we first provide the design of TECs for electronics cooling using a computational model and then experimentally validate the main predictions. Key device parameters such as device thickness, leg density, and contact resistance were studied to understand their influence on the performance of TECs. Our results show that it is possible to achieve high cooling power density through optimization of TE leg height and packing density. Scaling of TECs is shown to provide ultra-high cooling power density. [ABSTRACT FROM AUTHOR]

In the last few decades, considerable effort has been made to enhance the figure-of-merit (ZT) of thermoelectric (TE) materials. However, the performance of commercial TE devices still remains low due to the fact that the module figure-of-merit not only depends on the material ZT, but also on the operating conditions and configuration of TE modules. This study takes into account comprehensive set of parameters to conduct the numerical performance analysis of the thermoelectric cooler (TEC) using a Taguchi optimization method. The Taguchi method is a statistical tool that predicts the optimal performance with a far less number of experimental runs than the conventional experimental techniques. Taguchi results are also compared with the optimized parameters obtained by a full factorial optimization method, which reveals that the Taguchi method provides optimum or near-optimum TEC configuration using only 25 experiments against 3125 experiments needed by the conventional optimization method. This study also shows that the environmental factors such as ambient temperature and cooling coefficient do not significantly affect the optimum geometry and optimum operating temperature of TECs. The optimum TEC configuration for simultaneous optimization of cooling capacity and coefficient of performance is also provided. [ABSTRACT FROM AUTHOR]

Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the first two aspects are presented here, while an accompanying paper of this work reports findings on the third aspect. In this paper, grain microstructure evolution in the polycrystalline matrix with different template volume fractions and seed sizes is simulated. To quantitatively characterize the crystallographic texture development during templated grain growth processing, a numerical algorithm is developed to compute the diffraction peak intensities and Lotgering factor of the simulated polycrystals during grain microstructure evolution. This novel approach provides a direct link between phase field simulation and diffraction experiment. This computational study clarifies the effects of the template volume fraction and template seed size on the final grain microstructure and texture. It is found that, while the degree of crystallographic texture generally increases with increasing template volume fraction, it is the average distance between template seeds that plays an important role. This finding suggests that reducing the template seed size and shortening the seed distance is an effective way to achieve higher texture at a lower template volume fraction, which is highly desired for enhancing the piezoelectric properties of ferroelectric polycrystals. The computational results are compared with complementary experiments, where good agreement is obtained. [ABSTRACT FROM AUTHOR]

Traditional organic–inorganic halide perovskites (OIHPs), in which perovskites layers are separated by an organic spacer material, have been mainly explored for photovoltaics devices, but they also offer promises for nonlinear optics and quantum light applications. These attributes include (a) high quantum efficiency, (b) large binding energy of excitons in low-dimensional structures, (c) polarons of long coherence times at room temperature, and (d) a large spin–orbit coupling. OIHP systems can be engineered to have photoluminescence (PL) emissions from UV to IR regions, in addition to power conversion efficiencies, in excess of 24%. This class of materials offers broad tunability of its properties, through controlling the number of atomic layers in the quantum well, tuning the organic spacer thickness, or even engineering the composition with exotic dopants. In this work, we present PL and time-resolved PL measurements of quasi-2D BA2PbI4 and provide new insights on the temperature dependence of their excitonic dynamics and fine structures of their PL emissions. We observed long lifetimes, which can result from the formation of large polarons, screening the Coulomb interactions of the charge carriers and reducing the scattering of the carriers with charge defects. [ABSTRACT FROM AUTHOR]

Single crystals of 71PMN-6PZ-23PT [71Pb(Mg1/3Nb2/3)O3-6PbZrO3-23PbTiO3] oriented along the thickness direction (011) with and without Mn doping were grown by a solid-state single-crystal growth method, and pyroelectric properties of the crystals were investigated. Though the pyroelectric coefficient of a Mn doped crystal is not significantly higher than the un-doped one at room temperature (RT), a large enhancement was observed after 0.7 mol. % Mn doping at high temperatures (>100 °C). Furthermore, the FoMs for practical applications at RT, the Mn doped crystal showed large enhancement as compared to the un-doped one. The presented single crystals also yielded excellent figure of merit (FoM) values for pyroelectricity: Fi, Fv, and FD were 3.5 × 10−10 m V−1, 0.02 m2 C−1, and 2.68 × 10−5 Pa−1/2, respectively, at RT. The large pyroelectric response in the Mn-doped single crystal is attributed to the large ferroelectric polarization and low dielectric constant and dielectric loss. The demonstrated pyroelectric response in the Mn-doped 71PMN-6PZ-23PT single crystal shows that it exhibits excellent potential for various thermal sensor applications. [ABSTRACT FROM AUTHOR]

Two different templates (〈001〉 Ba6Ti17O40 and 〈111〉 BaTiO3) were used for synthesizing 〈111〉 textured tetragonal 0.6Pb(Mg1/3Nb2/3)O3-0.4PbTiO3(PMN-40PT) ceramics. It was found that a texture degree of 95% along 〈111〉 direction can be achieved by using only 1?vol.?% 〈111〉 BaTiO3 template due to its high chemical stability in the PMN-40PT matrix. The textured PMN-40PT ceramics with tetragonal structure exhibited an excellent temperature stability of piezoelectric properties due to the absence of intermediate phase transitions between room temperature and the Curie temperature. Unlike the single crystal counterpart, the effect of 〈111〉 grain orientation in the textured PMN-40PT ceramic on enhancing the macroscopic piezoelectric response was not significant in spite of its giant local piezoresponse. We provide detailed discussions on the nature of piezoelectric response in the 〈111〉 textured tetragonal PMN-40PT ceramic with "3T" engineered domain configuration and resultant strategy to realize high performance piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

This study provides comprehensive analysis of the structure-performance relationships in cantilever-type piezoelectric energy harvesters. It provides full understanding of the effect of all the practical global control variables on the harvester performance. The control variables considered for the analysis were material parameters, areal and volumetric dimensions, and configuration of the inactive and active layers. Experimentally, the output power density of the harvester was maximum when the shape of the beam was close to a square for a constant bending stiffness and a fixed beam area. Through analytical modeling of the effective stiffness for the piezoelectric bimorph, the conditions for enhancing the bending stiffness within the same beam volume as that of a conventional bimorph were identified. The harvester configuration with beam aspect ratio of 0.86 utilizing distributed inactive layers exhibited an giant output power of 52.5mW and power density of 28.5mWcm-3 at 30 Hz under 6.9ms-2 excitation. The analysis further indicates that the trend in the output power with varying damping ratio is dissimilar to that of the efficiency. In order to realize best performance, the harvester should be designed with respect to maximizing the magnitude of output power. [ABSTRACT FROM AUTHOR]

In this paper, single-phase multiferroic ceramics of (1 - x) BaTiO3 - x BiFeO3 (BT - x BFO) were synthesized by solid-solution method in the wide range of material composition (x = 0.025 - 1.0). The changes in crystal structure were confirmed via X-ray diffractions (XRD) and atomic pair distribution functions (PDFs). The room-temperature ME coupling was found to exhibit significant magnitude in the narrow composition window (x = 0.71 - 0.8) where the average crystal structure was found to be rhombohedral. Especially, the BT - 0.725 BFO ceramics containing local monoclinic distortions within rhombohedral phase were found to exhibit high room-temperature ME coefficient (αME) of 0.87 mV/cm·Oe with high piezoelectric properties (g33 = 18.5 × 10 mV m N-1 and d33 = 124 pC N-1). We believe that the high room-temperature ME coupling in single-phase lead-free BT-BFO ceramics provides a possibility of developing electrically or magnetically tunable thin-film devices. [ABSTRACT FROM AUTHOR]

The piezoelectric performance of polyvinylidene fluoride (PVDF) is shown to double through the controlled incorporation of carbon nanomaterial. Specifically, PVDF composites containing carbon fullerenes (C60) and single-walled carbon nanotubes (SWNT) are fabricated over a range of compositions and optimized for their Young's modulus, dielectric constant, and d31 piezoelectric coefficient. Thermally stimulated current measurements show a large increase in internal charge and polarization in the composites over pure PVDF. The electromechanical coupling coefficients (k31) at optimal loading levels are found to be 1.84 and 2 times greater than pure PVDF for the PVDF-C60 and PVDF-SWNT composites, respectively. Such property-enhanced nanocomposites could have significant benefit to electromechanical systems employed for structural sensing, energy scavenging, sonar, and biomedical imaging. [ABSTRACT FROM AUTHOR]

Crystallographic grain-oriented ceramics (also referred to as textured ceramics) are known to exhibit a high soft piezoelectric response. However, the role of texturing in hard piezoelectric materials is not well understood and it has been difficult to obtain a balance of hard and soft properties in the same material. Here, we investigate the hard and soft piezoelectric behavior of [001]PC-textured 0.05Pb(Mn1/3Sb2/3)O3-0.95[0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3] (PMnS-PMN-PZT) ceramics to illustrate the influence of texturing degree. The results demonstrate that textured PMnS-PMN-PZT ceramics exhibit a 170% higher longitudinal mode piezoelectric coefficient (d33) with only 16% reduction in the mechanical quality factor (Qm). Random PMnS-PMN-PZT ceramics were found to exhibit a d33 of 259 pC/N and a Qm of 982, while textured ceramics sintered at the same temperature demonstrated a d33 of 445 and a Qm of 824. Electric field dependent x-ray diffraction is utilized to confirm the existence of internal bias generated from defect dipoles, providing the signature for hard behavior. Temperature dependent measurement of d33 and Qm for textured PMnS-PMN-PZT ceramics indicated high stability up to 120 °C. [ABSTRACT FROM AUTHOR]

The elementary basis of intelligence in organisms with a central nervous system includes neurons and synapses and their complex interconnections forming neural circuits. In non-neural organisms such as slime mold with gel-like media, viscosity modulation enables adaptation to changing environments. At a larger scale, collective intelligence emerges via social interactions and feedback in animal colonies. Learning and memory are therefore multi-scale features that evolve as a result of constant interactions with the environment. There is growing interest in emulating such features of intelligence in computing machines and autonomous systems. Materials that can respond to their environment in a manner similar to organisms (referred to as "organismic materials") therefore may be of interest as hardware components in artificial intelligence machines. In this brief review, we present a class of semiconductors called correlated oxides as candidates for learning machines. The term "correlated" refers to the fact that electrons in such lattices strongly interact and the ground state is not what is predicted by classical band theory. Such materials can undergo insulator–metal transitions at near ambient conditions under external stimuli such as thermal or electrical fields, strain, and chemical doping. Depending on the mechanism driving the transition, intermediate states can be metastable with different volatilities, and the time scales of phase change can be controlled over many orders of magnitude. The change in electronic properties can be sharp or gradual, leading to digital or analog behavior. These properties enable the realization of artificial neurons and synapses and emulate the associative and non-associative learning characteristics found in various organisms. We examine microscopic properties concerning electronic and structural transitions leading to collective behavior and theoretical treatments of the ground state and dynamical response, showcasing VO2 as a model system. Next, we briefly review algorithms designed from the plasticity demonstrated by phase changing systems. We conclude the brief review with suggestions for future research toward realizing non-von Neumann machines. [ABSTRACT FROM AUTHOR]

Polycrystalline Pb(Zr0.52Ti0.48)O3 (PZT) thick films (thickness ∼10 μm) were successfully fabricated by using a novel aerosol deposition technique on Si wafer, sapphire, and single crystal yitria stabilized zirconia (YSZ) wafer substrates with Pt electrodes and their dielectric, ferroelectric, and piezoelectric properties, and in-plane stresses were investigated. The films with different stress conditions were simply controlled by the coefficient of thermal expansion (CTE) misfit of PZT films and substrates. The results showed that the films bearing in-plane compressive stress deposited on the YSZ and sapphire substrates have superior dielectric, ferroelectric (∼90%), and piezoelectric (>200%) properties over that of the Si wafer. Among these three substrates, YSZ shows superior properties of the PZT films. However, films on Si wafer with tensile stress present lower properties. We believed that in-plane compressive stresses within the films are benefited, the formation of c-domain parallel to the thickness direction resulting in the higher piezoelectric properties. These results suggest that the properties of polycrystalline PZT thick films can be adjusted by simply choosing the substrates with different CTEs. [ABSTRACT FROM AUTHOR]

In this paper, we describe an analytical model to define the temperature-time- transformation (TTT) diagram of sol-gel deposited Pb(Zr,Ti)O3 thin films on platinized silicon substrates. Texture evolution in film occurred as the pyrolysis and thermal annealing conditions were varied. We demonstrate that the developed model can quantitatively predict the outcome of thermal treatment conditions in terms of texture evolution. Multinomial and multivariate regression techniques were utilized to create the predictor models for TTT data. Further, it was found that multinomial regression can provide better fit as compared to standard regression and multivariate regression. We have generalized this approach so that it can be applied to other thin film deposition techniques and bulk ceramics. [ABSTRACT FROM AUTHOR]

In this paper, we report the dielectric and ferroelectric response of compositionally graded bilayer and trilayer composites consisting of BaTiO3 (BT) and 0.975BaTiO3-0.025Ba(Cu1/3Nb2/3)O3 (BTBCN). Two types of graded bilayer samples were synthesized, one with same thickness of BT and BTBCN while other with different layer thicknesses. The graded trilayer sample consisted of BT layer sandwiched between two BTBCN layers of equal thickness. Scanning electron microscopy and transmission electron microscopy images showed a sharp interface with needle-shape domains across the interface. The domain size on BT side was found to be larger than that on BTBCN side. The temperature dependence of dielectric response for all composite systems was found to exhibit shifting in characteristic Curie peak compared to constituent material which was associated to coupling between layers. Moreover, the differences in grain size, tetragonality, domain mobility of each layer was found to perturb the electrical response of composite. The polarization mismatch between uncoupled BT and BTBCN established internal electric field in composite specimen and defined new polarization states in each layer by perturbing free energy functional of the composite specimen. Dynamic hysteresis behaviors and power-law scaling relations of all specimens were determined from polarization-electric field hysteresis loop measurements as a function of frequency. All systems were found to exhibit similar dynamic scaling relationships. Hysteresis area , Pr, and EC decreased with increasing frequency due to delayed response but increased with increasing applied electric field due to enhancement of driving force. Trilayer system was found to exhibit strong internal-bias field and double hysteresis behavior. The coupling effect resulting due to polarization mismatch between layers had substantial influence on the dynamic hysteresis behavior and power-law scaling relations. [ABSTRACT FROM AUTHOR]

We report the magnetic field sensitivity results on five layer structure given as Metglas/Terfenol-D/ PMN-PZT/Terfenol-D/Metglas, where PMN and PZT correspond to Pb(Mg1/3Nb2/3)O3 and Pb(Zr,Ti)O3, respectively. The piezoelectric constant (d33) of poled PMN-PZT was found to be 1600 pC/N with dielectric constant of 5380 at 1 kHz. The sensitivity measurements were conducted after attaching individual layers in the laminate clearly delineating the effect occurring in the response. The magnetoelectric response for this five layer structure at 1 kHz was found to be 5 V/cm Oe at dc bias field of 1000 Oe under an ac drive of 1 Oe. At 1 kHz frequency, the sensor was able to deterministically measure step changes of 500 nT while at 10 Hz we can clearly identify the sensitivity of 1 μT. These results are very promising for the cheap room-temperature magnetic field sensing technology. [ABSTRACT FROM AUTHOR]

Rising demands in design of metamaterials requires better understanding of coupling phenomena in composite systems. Materials exhibiting product properties have effective magnitude of physical constants surpassing those of naturally existing materials. In this manuscript, we conduct numerical modeling of laminated terfenol-D/PZT/terfenol-D magnetoelectric composites with sandwich structure coupled through elastic interactions across the bonding layer. Developed magnetoelectric model couples the piezoelectric and magnetostriction constitutive equations with Langevin theory for simulating the saturated elastic response in composites. Simulated results were found to be in good agreement with the experimental results. Based upon the developed model we predict 17% improvement of magnetoelectric coefficient for sandwich structure through proper rotation of polarization in individual layers. [ABSTRACT FROM AUTHOR]

We report results on a dimensionally gradient magnetoelectric (ME) sensor that demonstrates high performance over a wide frequency range and a magnetic dc bias operating in the longitudinal-transversal mode. The design of the sensor is based on a piezoelectric bimorph structure and utilizes a laminate configuration with Pb(Zn1/3Nb2/3)0.2(Zr0.5Ti0.5)0.8O3 and Metglas as material layers. The wide-band behavior was characterized by a flat ME response over a wide range of magnetic dc biases corresponding to 60–215 Oe and frequencies corresponding to 7–22 kHz. By using tip mass, the wide-band frequency response was shifted to a lower frequency range of 5–14 kHz. The results show that the operating frequency range of the sensor can be easily shifted by changing the tip mass at the end of the composite. [ABSTRACT FROM AUTHOR]

We report the success in fabricating clamped, “island,” and freestanding 10 μm thick piezoelectric films using aerosol deposition. The deposition was conducted at room temperature by impinging the piezoelectric particles flowing through the nozzle onto platinized silicon (Pt/Ti/SiO2/Si) substrate and crystallization was conducted by annealing at 700 °C. Freestanding films were synthesized by increasing the cooling rate from annealing temperature to room temperature which resulted in large internal stress between the substrate and film interface. Dielectric and ferroelectric characterizations showed enhanced ferroelectric performance of freestanding films as compared to continuous or clamped film which was associated to increased domain contribution due to decrease in degree of clamping as further confirmed by piezoforce microscopy. [ABSTRACT FROM AUTHOR]

We present a general rule for the perovskite oxide ceramics: “A large piezoelectric constant in ABO3 perovskite ceramics can be obtained by tuning the weight ratio of A and B sites, WA/WB or WB/WA, to 3. Piezoelectric constant decreases significantly when WA/WB or WB/WA is in the range of 0.5–2.0, termed as forbidden zone.” A comparative analysis was conducted for broad range of materials demonstrating the applicability of proposed rule. Further based on this rule optimized compositions in BaTiO3 and alkali niobate based systems were developed. Polycrystalline ceramics in modified BaTiO3 system were found to exhibit longitudinal piezoelectric coefficient (d33) of 330 pC/N, while alkali niobate ceramics showed d33 of 294 pC/N. [ABSTRACT FROM AUTHOR]

In this study, we present a broadband magnetoelectric (ME) sensor design comprising of Metglas and piezoelectric ceramic laminate composite. A systematic study was conducted to elucidate the role of various composite variables toward the ME response [longitudinal-transverse (LT) mode] over the applied range of magnetic dc bias. The broadband behavior was characterized by flat ME responses over a wide range of magnetic dc bias at frequency of 1 kHz. The variation in ME coefficient as a function of magnetic dc bias was found to be significantly dependent on the size and shape of the laminate composites, the number of Metglas layers, and composite structure of sandwich versus unimorph. By adjusting these variables, we were able to achieve near-flat ME response over a magnetic bias range of 90–220 Oe. ME coefficient was also measured as a function of frequency, and at electromechanical resonance the peak value was found to be almost independent of applied magnetic bias in the range of 90–220 Oe. [ABSTRACT FROM AUTHOR]

By using coarse graining model, the dependence of magnetoelectric (ME) coupling on the mutual orientations of magnetic and electric fields with respect to the orientation of layers in polycrystalline multiferroic laminates is investigated. It is shown that the ME coefficient, described by polarization change in response to the applied magnetic field, is proportional to the trace of effective piezomagnetic strain tensor projected onto laminate interfaces. The piezomagnetic strain significantly depends on the orientation of applied magnetic fields. The results obtained here demonstrate that the magnetoelectric effect in layered composites can be significantly improved by optimizing the configuration of applied electric/magnetic fields. [ABSTRACT FROM AUTHOR]

In this study, we report results on magnetoelectric (ME) core-shell Pb(Zr,Ti)O3 (PZT)-NiFe2O4 (NF) particulate nanocomposites. NF particles forming the shell had size in range of 20–30 nm. The grain size of sintered nanocomposites was found to be in the range of 500–800 nm. The sintered nanocomposite exhibited piezoelectric coefficient (d33) of 60 pC/N, dielectric constant of 865, and ME coefficient of 195 mV/cm Oe. High ME coefficient was observed for wide range of dc bias magnetic field. This approach of fabricating layered composite has a promise to provide large ME coefficients in particulate sintered structures. [ABSTRACT FROM AUTHOR]

Trilayer composites consisting of 0.9Pb(Zr0.52Ti0.48)O3–0.1Pb(Zn1/3Nb2/3)O3 (0.9 PZT-0.1 PZN) and Ni0.6Cu0.2Zn0.2Fe2O4 (NCZF) in the configuration NCZF-(0.9 PZT-0.1 PZN)-NCZF were synthesized using pressure assisted sintering. Composites with optimized magnetostrictive to piezoelectric thickness ratio showed a high magnetoelectric (ME) coefficient of 525 mV/cm Oe. Further enhancement in the magnitude of ME coefficient was obtained (595 mV/cm Oe) when the angle of applied dc magnetic field was changed to 45°. Changing the intermediate piezoelectric layer from single to trilayer stack geometry configuration leads to the realization of giant ME response of 782 mV/cm Oe in sintered composites. [ABSTRACT FROM AUTHOR]

This study reports the low frequency magnetoelectric (ME) response of the sintered composites comprising of a piezoelectric phase Pb(Zr0.52Ti0.48)O3 (PZT) and magnetostrictive phases NiFe1.9Mn0.1O4 (NFM) and Ni0.8Zn0.2Fe2O4 (NZF) with varying ferrite contents of 3, 5, 10, 15, and 20 mol %. It was found that the ME coefficient for the PZT-NZF samples shows considerably less scattering as a function of frequency and the composition 0.8PZT-0.2NZF exhibited a flat response in the range of 10–100 Hz with a magnitude of 220 mV/cm Oe. This composition was used to design the magnetic field anomaly detector mounted in front of a global positioning system (GPS) controlled vehicle. The results from the vehicle test clearly demonstrate the feasibility of using sintered ME composites for magnetic field detection in the noisy environment. [ABSTRACT FROM AUTHOR]

This study reports the discovery of two perovskite materials Ba(Li[SUB1/4]Nb[SUB3/4])O[SUB3] (BLN) and Ba(Cu[SUB1/3]Nb[SUB2/3])O[SUB3] (BCN). BLN has a cubic symmetry at room temperature. The magnitude of dielectric constant at room temperature is of the order of 41. The dielectric spectrum of BLN exhibits a U shaped curve with a flat bottom. This flat region occurs in the temperature range of 200 - 300°C and the magnitude of dielectric constant in this region is 40 with a 0 ppm/°C temperature coefficient of permittivity. These characteristics appear to be very promising for microwave applications. BCN has a tetragonal structure at room temperature with a high tetragonality of 3.5%. The tetragonal symmetry is maintained until 600°C where the structure changes to cubic phase. Based upon the x-ray diffraction analysis, dielectric and electromechanical measurements of the BCN-PbTiO[SUB3] solid solutions it is predicted that BCN is a ferroelectric with high Curie temperature. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectric xBiScO[sub 3]-yBiGaO[sub 3]-(1-x-y)PbTiO[sub 3] (BS-BG-PT) single crystals were successfully grown using the high temperature solution method. The dielectric constant (K) of tetragonal crystals at room temperature was determined to be 500-600 with dielectric loss tangents less than 0.3% at a frequency of ∼1 kHz. The Curie temperature T[sub c] was found to be around ∼420°C, with longitudinal piezoelectric coefficient of ∼300 pC/N for 〈001〉 oriented tetragonal crystals. The remnant polarization P[sub r] was 46 µC/cm² with a coercive field E[sub c] of 43 kV/cm at 1 Hz and dc field of 60 kV/cm. Based on dielectric and polarization measurements, it was found that the low frequency regime was dominated by a space charge conduction mechanism. A space charge model is developed which correlates the polarization with the dielectric relaxation. The relaxation time on the order of ∼2.2 ms was obtained in the BS-BG-PT single crystal using this model. [ABSTRACT FROM AUTHOR]

The functional form of the time decay of the remanent polarization under high-electrical drives, known as fatigue, has been derived for relaxor piezoelectric materials based on the hierarchical relaxation process, typical of disordered systems such as random-field and glassy states and is given in terms of normalized remanent polarization (&Pmacr;[sub r]) as &Pmacr;[sub r](t)=&Pmacr;[sub o]t[sup -x] exp[-c(t/τ)[sup β]]. This function was verified by fitting the dynamics of the fatigue behavior in 0.92Pb(Zn[sub 1/3]Nb[sub 2/3])O[sub 3]-0.08 PbTiO[sub 3] (PZN-PT) relaxor-based piezoelectric system. Mn modification of a PZN-PT single crystal improved the fatigue behavior by slowing down the relaxation processes and pinning the domain wall motion. [ABSTRACT FROM AUTHOR]

Polarization switching and dielectric temperature behavior have been investigated in 0.55Pb(Yb[sub 1/2]Nb[sub 1/2])O[sub 3]–0.45PbTiO[sub 3] (PYN–PT) single crystals. These compositions are of interest owing to their unusually high Curie temperature and high coercive fields. The dielectric permittivity was determined as function of temperature and the polarization was measured as a function of applied field for different drive frequencies. Analysis of the experimental results with a random-field model was found to show similar trends to recent reports for the Pb(Mg[sub 1/3]Nb[sub 2/3])O[sub 3] relaxor materials. The frequency dispersion of the maximum in dielectric spectra, T[sub max], was also analyzed with the Vogel–Fulcher relation yielding a high freezing temperature of 577 K. Polarization behavior was found to follow a stretched exponential time dependence and a fractal dimension of ∼2.2 was obtained. It is proposed that the polar cluster state in PYN-PT single crystals do not freeze in random orientations but rather arrange locally in preferred configurations. The fraction of the clusters decreases under increasing external field drive, resulting in the formation of the percolated network at higher fields. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this article, we report the dielectric and piezoelectric properties of Mn modified 0.92Pb(Zn[sub ⅓]Nb[sub ⅔])O[sub 3] - 0.08PbTiO[sub 3] (PZNT) single crystals. The crystals were grown by the modified-flux method. Mn substitution resulted in enhanced mechanical quality factor, Q[sub m], and a moderate increment in the rhombohedral to tetragonal phase transition temperature with increasing Mn composition. Investigation of the role of Mn in PZNT was performed on the basis of dielectric, piezoelectric and polarization versus electric hysteresis measurements. It was found that the improved Q[sub m] is obtained because of the induction of the "hard" characteristics into the PZNT single crystal. High Q[sub m] piezocrystals are being developed for high power applications. [ABSTRACT FROM AUTHOR]

We synthesized epitaxial BTO-BFO heterostructure with decreased leakage and simultaneously improved the multiferroic properties. This study provides new direction for ferromagnetic resonance studies, in high quality BTO-BFO films grown on LSMO. We observed small Gilbert damping (α=0.004) and the absence of large inhomogeneous broadening, in a film with 80 nm thickness of BTO-BFO on LSMO (110). This fact offers opportunities for employing this material system for spin transfer in multifunctional materials where controlling magnetization by a flow of spin angular momentum, or spin current, is crucial toward developing nanoscale spin-based memory and devices. Magnetic insulators, such as BTO-BFO on LSMO, are potentially excellent candidates for pure spin current without the existence of charge current. [ABSTRACT FROM AUTHOR]

Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the "Elephant" two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes. [ABSTRACT FROM AUTHOR]

Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4×25.4mm² area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density. [ABSTRACT FROM AUTHOR]

The shear mode piezoelectric properties of Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) ceramic with 72% ⟨111⟩ texture were investigated. The piezoelectric anisotropic factor d 15/d 33 was as high as 8.5 in ⟨111⟩ textured ceramic as compared to 2.0 in random counterpart. The high d15/d33 indicates the "rotator" ferroelectric characteristics of PMN-PZT system and suggests that the large shear piezoelectric response contributes towards the high longitudinal piezoelectric response (d33) in non-polar direction (d33 = 1100 pC/N in ⟨001⟩ textured ceramic vs. d33 = 112 pC/N in ⟨111⟩ textured ceramic). [ABSTRACT FROM AUTHOR]

A highly dense, 4 lm-thick Pb(Zr,Ti)O3 (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longerwavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas filmcomposites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices. [ABSTRACT FROM AUTHOR]

Local atomic structure of KxNa(1-x)NbO3 with 0.0 ≤ x ≤ 1.0 was studied using atomic Pair Distribution Function analysis based on x-ray diffraction. Powdered crystals were found to exhibit a re-entrant behavior by being orthorhombic (Amm2) for x ≤ 0.42, monoclinic (Pm) for 0.42 ≤ x ≤ 0.63 and again orthorhombic (Amm2) for x > 0.63. Non-centrosymmetric structure of NaNbO3 (Amm2) was also evident in the piezoresponse force microscopy analysis revealing the presence of the ferroelectric domains and switching behavior. Lowering of the crystallographic symmetry for 0.42 ≤ x ≤ 0.63 is discussed in terms of differences in the sizes of Na+ and K+ ions and Na-O and K-O bond lengths. Besides being a bridging phase, as suggested by the previous studies on lead-based compositions, present study suggests that lower symmetry monoclinic phase of compositionally disordered perovskite solid solutions could also be a manifestation of the difference in the sizes of constituent ions and bond lengths. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate a co-fired magnetoelectric (ME) laminate consisting of piezoelectric/magnetostrictive/piezoelectric layers with unipoled piezoelectric transformer structure. The ME transformer was characterized by quantifying the voltage gain variation and resonance frequency shift as a function of applied DC magnetic field. We delineate the magnetic tunability feature by considering the magnetoelectric coupling and delta-E effect, where E represents the modulus of magnetic material. The ME response of the composite structure was found to be 473mV/cm. Oe exhibiting DC field sensitivity of 100 nT under AC field of 1 Oe at 1 kHz. At a magnetic bias of 60 Oe, the transformer exhibited large frequency tunability of the order of 1.4Hz/Oe. These results present significant advancement towards developing on-chip magnetic-field-tunable devices. [ABSTRACT FROM AUTHOR]

We demonstrate a 33-mode piezoelectric structure with zigzag shape for high sensitivity magnetoelectric laminates. In contrast to the 33-mode macro fiber composite (MFC), this zigzag shape piezoelectric layer excludes epoxy bonding layer between the electrode and piezoelectric materials, thereby, significantly improving the polarization degree, electromechanical coupling, and the stability of loss characteristics. The polarization degree was monitored from the change in phase angle near resonance, and the loss stability was determined from the changes in dielectric loss and rate of capacitance variation defined by (C - Cf)/Cf, where C is capacitance at a given frequency and Cf is capacitance at 100 Hz. Magnetoelectric composite with zigzag patterned piezoelectric layer was found to exhibit giant magnetoelectric response both in low frequency off-resonance region (6.75Vcm-1 Oe-1 at 1 kHz) and at anti-resonance frequency (357Vcm-1 Oe-1). [ABSTRACT FROM AUTHOR]

〈001〉pc textured K0.5Na0.5NbO3 (KNN) ceramic was found to exhibit a 65% improvement in the longitudinal piezoelectric response as compared to its random counterpart. Piezoresponse force microscopy study revealed the existence of larger 180° and non-180° domains for textured ceramic as compared to the random ceramic. Improvement in piezoresponse by the development of 〈001〉pc texture is discussed in terms of the crystallographic nature of KNN and domain morphology. A comparative analysis performed with a rhombohedral composition suggested that the improvement in longitudinal piezoresponse of polycrystalline ceramics by the development of 〈001〉pc texture is determined by the crystal structure. [ABSTRACT FROM AUTHOR]

We report the physical behavior of self-biased multi-functional magneto-mechano-electric (MME) laminates simultaneously excited by magnetic and/or mechanical vibrations. The MME laminates composed of Ni and single crystal fiber composite exhibited strong ME coupling under Hdc = 0 Oe at both low frequency and at resonance frequency. Depending on the magnetic field direction with respect to the crystal orientation, the energy harvester showed strong in-plane anisotropy in the output voltage and was found to generate open circuit output voltage of 20 Vpp and power density of 59.78 mW/Oe² g² cm³ under weak magnetic field of 1 Oe and mechanical vibration of 30 mg, at frequency of 21 Hz across 1 MΩ2 resistance. [ABSTRACT FROM AUTHOR]

We report a magnetoelectric energy harvester structure that can simultaneously scavenge magnetic and vibration energy in the absence of DC magnetic field. The structure consisted of a piezoelectric macro-fiber composite bonded to a Ni cantilever. Large magnetoelectric coefficient ∼50 V/cm Oe and power density ∼4.5 mW/cm3 (1 g acceleration) were observed at the resonance frequency. An additive effect was realized when the harvester operated under dual-phase mode. The increase in voltage output at the first three resonance frequencies under dual-phase mode was found to be 2.4%, 35.5%, and 360.7%. These results present significant advancement toward high energy density multimode energy harvesting system. [ABSTRACT FROM AUTHOR]

Grain orientation, BaTiO3 heterogeneous template content, and electrode materials are expected to play an important role in controlling the polarization fatigue behavior of <001> textured Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics. A comparative analysis with randomly oriented ceramics showed that <001> grain orientation/texture exhibits improved fatigue characteristics due to the reduced switching activation energy and high domain mobility. The hypothesis was validated from the systematic characterization of polarization-electric field behavior and domain wall density. The defect accumulation at the grain boundary and clamping effect arising from the presence of BaTiO3 heterogeneous template in the final microstructure was found to be the main cause for polarization degradation in textured ceramic. [ABSTRACT FROM AUTHOR]

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]PC textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature Td in poled samples resulted from a tetragonal → pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on Td: ac drive decreased the Td, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature. [ABSTRACT FROM AUTHOR]

Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate self-biased magnetoelectric effect in homogenous two-phase magnetostrictive-piezoelectric laminates. Our results illustrate the method for tuning the magnitude of self-bias effect and provide understanding behind the hysteretic changes. We model this phenomenon by considering the magnetization hysteresis with shape-induced demagnetization effect. The self-biased response was found to be directly related to the nature of magnetization and can be tuned by variation in demagnetization state and the resultant differential magnetic flux distribution. These results present significant advancement toward development of AC magnetic field sensor and magnetoelectric composite based on-chip devices by eliminating the need for DC bias. [ABSTRACT FROM AUTHOR]

[001]-textured Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics were synthesized by using templated grain growth method. Significantly high [001] texture degree corresponding to 0.98 Lotgering factor was achieved at 1 vol. % BaTiO3 template. Electromechanical properties for [001]-textured PMN-PT ceramics with 1 vol. % BaTiO3 were found to be d33 = 1000 pC/N, d31 = 371 pC/N, &eh;r = 2591, and tanδ = ∼0.6%. Elastoelectric composite based modeling results showed that higher volume fraction of template reduces the overall dielectric constant and thus has adverse effect on the piezoelectric response. Clamping effect was modeled by deriving the changes in free energy as a function of applied electric field and microstructural boundary condition. [ABSTRACT FROM AUTHOR]

Highly dense 1 μm-thick piezoelectric film was deposited on magnetostrictive substrate [platinized nickel-zinc ferrite (NZF)]. A strong magnetic coupling between the piezoelectric film and magnetostrictive NZF substrate was measured exhibiting the maximum magnetoelectric (ME) coefficient on the order of 140 mV/cm Oe at the conditions of HDC = 50 Oe and HAC = 1 Oe at f = 1 kHz. This giant ME coupling under low DC magnetic field condition is attributed to effective elastic coupling. A rotation-type dynamic strain distribution was observed on the PZT film surface which provides information about the nature of elastic coupling. [ABSTRACT FROM AUTHOR]